My (new to me) 99 XJ 2 door has an interesting quirk. It may just be an XJ thing, You XJ quirk solving pros can let me know what you think.

Here's the stats... Stock axles with lockers (locker may be the issue) Unknown brand of long arm front lift. looks like about 6 inches to me. Lift springs in the back with normal length aftermarket shackles. I've 'nut and bolted' everything, checked all the bushings and rod ends. No visible cracks or strange movements at the frame, steering box, or at the axle brackets, (loaded or unloaded). I've put both front tires against a wall and steered it over to watch for unusual movements, there were none. It has fresh 1 ton steering linkage. I've changed the air pressures up and down, alignment is dead on, and rotated the 35 inch General Grabbers... It drives the same. The drag link and the pan hard bar are at equal/even angles. It flexes and climbs very well, with no steering drama. Very predictable off road.

OK. Here's the issue... When you are on gas to get up to speed (45-55 MPH) and let off the throttle... The front jumps left or right. Its like its unloading something, and it just goes where it wants to. (unloading may be the key word here) Is this normal with lifted and locked XJ's? You can drive it like this, but its just strange. Its like riding a spooked horse, you aren't sure which way its going to go.

Any experienced opinions would be appreciated.

 

Pics of front end components. As many as you care to take

 

Absolutely this

 

Pics of the front end. We checked the square front to rear, and the alignment was dead on. Caster seems right, it returns to center very well.

 

So first thing I would address. Your passenger upper control arm mount needs to be boxed in. I can already see it bowing/folding in. This leads to both those radius arms fighting the axle as the suspension articulates.

Next thing I would work at is your steering angle. While the track bar and drag link are looking pretty parallel, the force going into that steering box ?which doesnt look plated or braced? Is a giant lever. I can see your still running a factory pitman arm which is good because that reduces the deflection that the longer drop pitman arms cause.

Look into an over the knuckle steering configuration and then also moving the track bar mount on the axle higher as well to maintain that matched angle

 

Not the most methodical or theory-based answer, but I have found a front sway bar helps keep things of this nature under control. I very much prefer how my Jeep handles on the road with a sway bar. I have a similar steering/suspension setup as you.

 

In conjunction with the other good suggestions, I think you are right. I bought it this way and im unraveling the mysteries that came with it. I had been thinking sway bars would settle it down a bit. Thanks!

 

Thanks! Sounds like solid advice. I am building a set of axles for it as we speak. The front will have a Barnes truss and mounts on them so that should take care of the weak mounts. I will box in that upper control arm mount in the mean time. The Dana 60 will flatten out the steering angles with the high steer knuckles.
What are your thoughts on reinforcing the steering box mount and other areas? I will probably be adding hyro assist.

Thanks again... Tom

 

This is a pretty affordable and popular option now.


Otherwise a steel plate steering box spacer for inside of unibody


And also plating the outside of the unibody really helps.

There's also multiple layers of factory sheet metal that makeup the unibody rails up front. Welding all those layers together vs the rosette welds that currently makeup the structure is another good idea.

 

Is the upper radius arm end, the one the connects back to the lower end, a Heim joint? If so the binding of the radius arms when under the load from acceleration, which is usually not noticed because upper radius arms need soft bushings on each side, is bending the upper axle mount like previously mention. This little movement is probably very noticeable at 40+ mph and accelerating.

 

The dana 60 swap with true crossover steering will be a huge factor in making your jeep drive well. If youve done your research and know what your doing.
if you havent you might actually make it drive worse than it currently does.

If it where mine i would increase link seperation alittle to help dive under deceleration and braking. I found running more seperation with 35s is better.

Since you have a 60 youl probly be on 37s or 40s pretty quick. Link seperation should be about 30% of tire diameter.

yes.

I am running more link seperation than stock have multiple link mounting points to play with different driving characteristics.

In the end link seperation, castor numbers n **** mean nothing its how it drives on the rd and trail that matters. Knowing what changes do is far more beneficial than the numbers.

M9st important never trust any numbers spit put like castor on jeep forumn you have no clue how they arrived at this said number, if they even knew how to measure it or if they even own a jeep at all.

Tune your **** and trust no one. And always when you can build adjustability in because its most likly wrong where you think its right.

 

FYI...I am looking at the Barnes truss mount for the front 60.
If I'm hearing you correctly... The distance between the bolt holes in the upper and lower front control arm mounts need to be 30% of the tire diameter. With a true 37 they should be 11.1 inches from center to center. Should there be an arc involved that bisects the two bolt holes?

 

No arc needed. Put the mounting points where they fit. My upper is alittle forward of the lowers.

If you had link seperation mounting points at 10.5 11.5 and 12.5 that would be perfect give you some driving characteristic tunability.

I run a 3 link i fabbed similar to stinky fabs 3 link no sway bars with king coilovers tuned by accutune

Steering is wj over the knuckles. The thing drives better rides better and handles better than a oem xj on the street then can blast the sage brush at 60

The custom set up is in a another playing feild than bolt on stuff everything is set up to work together

 

OK... Made a carboard pattern and plated the front of the UCA bracket with 1/4 plate. I also welded the inner parts of the factory bracket to the tube. I made the bottom of the reinforcement plate tie into the axle tube at the bottom (cant hurt). Ya'll were right, Its a pretty weak design from the factory.

I believe the rest of the issue is in the steep steering angle and the separation distance/angle of the upper and lower control arms). I will deal with that when I hang the 60's under it and brace the frame/steering box mount. Multiple mounting point holes sound like a good idea in the UCA bracket, to dial it in.

Thanks for the suggestions.

 

Heres mine for motivation.

It by far hands down is the best driving handling offroad capable small tire jeep in my town.

Options to go up or down a tire size. Aswell as steering incase i go to 3/4" drop pitman. I did all this first with no tunning options. Ive cut stuff off and started over multiple times. Its a ton of effort tunning with the welding machine when you could just undo a bolt and put it back in an inch higer or lower.


I slightly screwd up. This bracket is clearanced tp clear frame at full stuff vertical travel of both shocks at same time. Articulating it cleared